JPH04100876A - Heat-resistant coating material - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant coating material which gives a film excellent in heat resistance and free from occurrence of pinholes even at high temperature by dispersing or dissolving a carbosilane polymer, a silicone resin, an inorganic filler, and a glass frit having a specified softening point in an organic solvent. CONSTITUTION:A polycarbosilane [an organosilicon compound consisting mainly of bonding units of formula I (wherein R<1> is H or alkyl; R<2> is alkyl or phenyl)] and/or a polycarbosilastyrene [an organosilicon compound consisting of bonding units of formula I and those of formula II (wherein R<3> and R<4> are each H, alkyl or phenyl) and in some cases having a partially crosslinked linkage], a silicone resin (e.g. dimethylpolysiloxane), an inorganic filler, and a glass frit having a softening point of 400-600 deg.C are dispersed or dissolved in an organic solvent to give a heat-resistant coating material. This coating material can give a film excellent in heat resistance and free from occurrence or with remarkably controlled occurrence of pinholes even at high temperature.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a heat-resistant paint that can withstand use at high temperatures.

(Prior Art and its Problems) JP-A-62-235370 discloses a heat-resistant paint in which a polycarbosilane, a silicone resin, and an inorganic filler are dispersed or dissolved in an organic solvent.

The heat-resistant paint described in the above-mentioned publication can be baked in air, and the coating film obtained therefrom has the advantage of not only excellent heat resistance but also good corrosion resistance and impact resistance.

On the other hand, the coating film formed from the paint described in the above publication was
When exposed to temperatures above 00''C, the polycarbosilane undergoes volumetric shrinkage as it converts to inorganic matter, and pinholes can form that reach the substrate.

The pinholes that occur in this paint film limit its use in applications where it is exposed to corrosive gases, which is a problem that needs to be solved.

(Technical means for explaining the problem) The present invention is a heat-resistant paint that has excellent heat resistance and can provide a coating film in which pinholes are not generated or are significantly suppressed even at high temperatures. I will provide a.

According to the present invention, there is provided a heat-resistant paint in which polycarbosilane and/or polycarbosilastyrene, a silicone resin, an inorganic filler, and a glass frit having a softening point of 400 to 600°C are dispersed or dissolved in an organic solvent. be done.

The polycarbosilane in the present invention mainly has the following formula C
It is an organosilicon polymer consisting of carbosilane bonding units represented by I).

(In the formula, R' represents a hydrogen atom or an alkyl group, and R2 represents an alkyl group or a phenyl group.) The polycarbosilastyrene of the present invention has a bonding unit represented by the above formula (I) and the following formula (ff ) is an organosilicon polymer that is composed of silastyrene bond units, and in some cases has partially crosslinked bonds.

(In the formula, R3 and R4 each represent a hydrogen atom, an alkyl group, or a phenyl group.)
It can be prepared according to the method described in Japanese Patent No. 39617. The description of this publication is incorporated herein by reference.

In the following description, polycarbosilane and polycarbosilastyrene may be collectively referred to as "rcarbosilane polymer".

Specific examples of the silicone resin in the present invention include dimethylpolysiloxane, methylphenylpolysiloxane,
Pure silicone resins such as diphenylpolysiloxane, pure silicone resins, alkyd resins, polyester resins,
Examples include modified silicones reacted with modifying resins such as acrylic resins and epoxy resins.

The blending ratio of silicone resin is 10 parts of carbosilane polymer.
0 parts by weight, 10 to 900 parts by weight, especially 50 to 50 parts by weight
Preferably, it is 0 parts by weight. If the blending ratio of silicone resin is too small, the flexibility of the coating film will be reduced due to baking, and if the ratio is too high, the heat resistance and corrosion resistance of the coating film will be reduced due to baking.

As the inorganic filler in the present invention, at least one selected from oxides, borides, phosphates, silicates, silicides, borides, nitrides, and carbides is used. Examples include magnesium, calcium, barium,
Titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper, zinc, boron, aluminum, silicon oxides, carbides, nitrides, silicides, borides, lithium, sodium, potassium, magnesium, calcium or zinc. Examples include borates, phosphates, and silicates.

The blending ratio of the inorganic filler is preferably 10 to 900 parts by weight, particularly 50 to 500 parts by weight, per 100 parts by weight of the carbosilane polymer. By incorporating an inorganic filler, the adhesion of the coating film to the substrate during baking is improved, but if the proportion of the inorganic filler is too high, the flexibility of the coating film decreases.

Examples of the glass material for the glass lift in the present invention having a softening point of 400 to 600"C include phosphate glass, borosilicate glass, and lead glass. Among these, lead glass is toxic, so Heat-resistant paints containing these should be avoided for civilian applications, such as cooking utensils.On the other hand, phosphate glasses and borosilicate glasses are non-toxic and should therefore be used in all types of applications, including civilian ones. can be used.

Glass frit can be prepared according to a method known per se, in which molten glass is sprayed into water and cooled.

There are no particular restrictions on the particle size of glass frit, but
Generally, it is 2 to 20 μm.

The blending ratio of glass lift is 10 to 200 M parts, particularly 20 to 200 M parts, per 100 parts by weight of polymetallocarbosilane.
Preferably it is 100 parts by weight. If the blending ratio of glass flint is too small, the chemical resistance at high temperatures, that is, the durability against corrosive gases will not be sufficient, and if the ratio is increased too much, the flexibility of the coating will decrease.

When the softening point of the glass frit is lower than 400"C, the glass frit sometimes melts and aggregates during paint baking, which reduces the adhesion of the paint film and reduces the mechanical strength.The softening point is 600"C. If it is higher than C, the effect of preventing pinholes in the coating film will be reduced.

As the organic solvent in the present invention, any solvent can be used as long as it is capable of dissolving the carbosilane polymer and silicone resin. Specific examples include toluene, xylene, n-butanol, isobutanol, butyl acetate, mineral spirit, solvent naphtha, ethyl cellosolve, and cellosolve acetate.

The proportion of the organic solvent to be used varies depending on the type and blending proportion of the film-forming components, and can be appropriately determined by those skilled in the art in accordance with the disclosure of the present invention.

The heat-resistant paint of the present invention is applied to a metal base material or a non-metal base material such as ceramic or firebrick by means known per se such as a brush coater, a roll coater, spraying, or dipping, and then dried. Burned in.

The amount of heat-resistant paint applied is preferably 20 to 100 g/rrf. If the coating amount is too small, pinholes are likely to occur in the coating film, resulting in decreased corrosion resistance.

On the other hand, if the coating amount is excessively large, the coating film is likely to crack when exposed to high temperatures or cold/heat cycles.

The baking temperature is preferably 150°C or higher, particularly 200°C or higher. If the baking temperature is too low, the polymetallocarbosilane, which is one of the paint components, will not be sufficiently cured, resulting in a decrease in the strength of the coating film and its impact resistance. Incidentally, if the object to be coated is placed in a usage environment of 150° C. or higher after coating with the paint, the baking step may be omitted.

(Example) Examples and comparative examples are shown below. In the examples, unless otherwise specified, "1%" and "parts" refer to "% by weight" and "parts by weight J," respectively.

The heat resistance of the coating film was evaluated as follows. After keeping the object to be coated in an air oven at 1000°C for 200 hours, it was taken out of the oven and slowly cooled in the air, and then cross cuts with a pitch of 1 mm were made on the coating film using a cutter knife.
Adhesive cellophane tape was attached to this area, and the presence or absence of peeling of the paint film was examined after the tape was rapidly peeled off. The heat resistance was rated as "good" if no peeling of the coating film was observed, and the heat resistance was rated as "poor" if any peeling was observed.

The presence or absence of pinhole-like peeling portions in the coating film was evaluated as follows. After holding the object to be coated in open air for 200 hours at 1000''C, remove it from the oven and allow it to cool slowly. Then, salt water is sprayed on it for 200 hours, and whether or not corrosion has formed on the coating film is examined using a 50x microscope. I observed it.

Rust formation and blistering of the paint film were observed on those with pinhole-like peeling.

Reference Example 1 (Synthesis of polycarbosilane) 2.51 g of anhydrous xylene and 400 g of sodium were placed in a 51-meter three-hole flask and heated to the boiling point of xylene under a stream of nitrogen gas, and then 1.5 g of dimethyldichlorosilane was added. 1
It dripped in time. After the dropwise addition was completed, the mixture was heated under reflux for 10 hours to form a precipitate. This precipitate was filtered and washed first with methanol and then with water to obtain 420 g of white powder polydimethylsilane.

On the other hand, 750 g of diphenyldichlorosilane and 124 g of boric acid were heated at 100 to 120°C in n-butyl ether under a nitrogen gas atmosphere, and the resulting white resinous material was further heated in vacuum at 400°C for 1 hour.
530 g of polyborodiphenylsiloxane was obtained.

Next, 8.27 g of the above polyborodiphenylsiloxane was added to 250 g of the above polydimethylsilane and mixed, and the mixture was heated under a nitrogen stream in a 21 quartz tube equipped with a reflux tube for 35 minutes.
The mixture was heated to 0° C. and polymerized for 6 hours to obtain a polycarbosilane partially containing siloxane bonds.

After cooling the product, add xylene to take it out as a solution, filter it, and then evaporate the xylene to reduce the number average molecular weight to 1.
500 polycarbosilane was obtained.

Reference Example 2 (Synthesis of polycarbosilastyrene) Equimolar amounts of dichloromethylsilane and dichloromethylphenylsilane were mixed in a toluene solvent in the presence of a Na dispersed catalyst,
A polymerization reaction was carried out at 10°C to obtain polysilastyrene having a softening point of 86 to 94°C.

This polysilastyrene was heat-treated at 420°C for 15 minutes under reduced pressure to have a softening point of 175-185°C and a number average molecular weight of 450.
0 polycarbosilastyrene was obtained.

Example 1 100 parts of 50% xylene melt of polycarbosilane obtained in Reference Example 1, 50% of methylphenylpolysiloxane
Xylene solution (manufactured by Toho Silicone Co., Ltd., TSR-116)
100 parts, silicon carbide powder 100 parts, phosphate glass frit (manufactured by Nippon Ferro, 01-401-4l02
A heat-resistant paint was prepared by mixing 50 parts of xylene and 50 parts of xylene in a mixer.

Separately, a stainless steel plate (SOS 316L) with a thickness of 0.6 am was degreased with acetone as a base material and then air-dried.

Approximately 30μ of the heat-resistant paint is applied to the base material using a spray gun.
The film was coated to a thickness of m, baked in an air oven at 300°C for 25 minutes, and then slowly cooled.

The heat resistance of the resulting coating film was "good" and no pinhole-like peeling was observed.

Example 2 Example 1 was repeated except that 50 parts of borosilicate glass frit (manufactured by Nippon Ferro, 12-3615) was used in place of the borate glass frit.

The heat resistance of the resulting coating film was "good" and no pinhole-like peeling was observed.

Comparative Example 1 Example 1 was repeated except that a borate glass frit was wanted.

Although the heat resistance of the resulting coating film was "good", pinhole-like peeling was observed.

Example 3 Example 1 was repeated except that 100 parts of the 50% xylene solution of polycarbosilastyrene obtained in Reference Example 2 was used instead of the xylene solution of polycarbosilane.

The heat resistance of the resulting coating film was "good" and no pinhole-like peeling was observed.

Claims (1)

[Claims] Polycarbosilane and/or polycarbosilastyrene, silicone resin, inorganic filler, and a softening point of 400 to 60
A heat-resistant paint characterized by glass frit having a temperature of 0°C dispersed or dissolved in an organic solvent.